Matsya Purana — War of Devas and Asuras; Birth of Aurva Fire; Countering Tamasī Māyā through ...
दानवा दैवतैः सार्धं नानाप्रहरणोद्यताः समीयुर्युध्यमाना वै पर्वता इव पर्वतैः //
dānavā daivataiḥ sārdhaṃ nānāpraharaṇodyatāḥ samīyuryudhyamānā vai parvatā iva parvataiḥ //
The Dānavas, brandishing many kinds of weapons, closed in together with the gods, clashing in battle—like mountains colliding with mountains.
This verse does not discuss Pralaya; it depicts a Deva–Dānava battle, emphasizing the cosmic scale of conflict through the simile of mountains colliding.
Indirectly, it models the Purāṇic theme of steadfastness in one’s ordained role: as Devas and Dānavas meet decisively in combat, so a king is expected to confront threats with preparedness and courage, using appropriate means (weapons/strategy) when protection of order is at stake.
No Vāstu or ritual procedure is specified here; the only technical element is martial—“various weapons”—used to heighten the grandeur of the battle scene.